Philippians
King James Version (KJV)

“Being confident of this very thing, that he which hath begun a good work in you will perform it until the day of Jesus Christ:”
King James Version (KJV)
1:6 Being persuaded - The grounds of which persuasion are set down in the following verse. That he who hath begun a good work in you, will perfect it until the day of Christ - That he who having justified, hath begun to sanctify you, will carry on this work, till it issue in glory.
Php 1:6 Being confident of this very thing. So faithful have they been that he is confident that they will be faithful to the end. That he which hath begun a good work in you will perform [it]. God, who sent Paul to them with the gospel, began the good work. He will sustain them by his grace. Until the day of Jesus Christ. The day they are called to his presence.